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By J. A. Wallace

U. S. Steel's coal mining research activities are directed toward providing new or improved hardware and techniques to increase productivity or reduce cost. Because more than 80 percent of U. S. Steel's coal production is obtained from continuous miner sections, most of our research efforts are focused upon that mining system. Current and historical time study data show that our continuous miners only operate about 30 percent of the available face time. This limited equipment utilization is the result of the delays or interferences imposed by the non-coal-cutting phases of the continuous mining cycle. The most time consuming of these delays are: waiting-on-roof-support, tramming between alternate work locations, waiting-on-haulage-capacity, and in some mines waiting for excessive methane concentrations to clear. Because waiting on roof support is our most time consuming delay, several programs are underway simultaneously to address this problem. In one of these we are developing a patented microprocessor-based control method and apparatus to improve roof drilling performance. This increase is attained by using the microprocessor to adjust electrohydraulic valves which control drill thrust and rotation speed. The microprocessor is designed to continuously search for an optimum combination of thrust and drill rpm to maximize penetration rate at all times.

Jan 1, 1979

By R. Svensson

Mill linings play an important role in all comminution processes with tumbling mills. The selection of the lining profile and the lining material has a great impact on over-all grinding cost and mill throughput. The cost of the lining itself is minor in comparison with media cost, energy cost and the value of the material produced in the mill. The total scope must be considered when mill linings are selected. This paper presents case stories and explains the technology behind: -different lining profiles in rubber and steel -OREBED magnetic lining -Steel-cap rubber lining

Jan 1, 1994

By Olivier Martin

In busy and historic cities, traditional open box metro stations are becoming outrageously difficult, unacceptable for the citizen and uneconomical. Hybrid stations provide an interesting alternative. In-house experience of Gautrain (South Africa), West bay (Qatar), Cairo line 3A (Egypt), and Melbourne (Australia) all aim to reduce disturbance to the city and its inhabitants during construction. Constructed in rock or in deep soil under water table, they take advantages of the latest construction techniques from cement grouting to freezing, and from traditional excavation of cavern to large tunnels constructed by sophisticated tunnel boring machines (TBM). Today, they form the ultimate construction challenge.

Jun 13, 2021

By M. G. Schulz

Mining of molybdenum at Questa, New Mexico has been accomplished by block cave methods since August, 1983. As caving progresses, a periodic geologic evaluation is made of the rock-types present in finger raises on the Grizzly Level of the mine. The production maturity of the cave can be monitored by relating this data to geologic cross-sections through the ore body. The draw point mapping program is a simple and effective tool that is used in making draw control decisions at Questa.

Jan 1, 1985

By Jiachen Wang, Nan Wang, Yang Li

The close-multiple coal seam is an important component of China’s coal resources and plays a key role in total coal reserves. However, the overburden movement in the mining process of close-multiple coal seams is usually extensive, which is seriously affected by overmining. It is therefore essential to study the mechanism of roof breakage, the relationship between the shield and the surrounding rock, and the mechanism of overburden movement to ensure the safe operation and the efficient exploitation of close-multiple coal seams. This work first proposes a technical route for intelligent ground control. Second, the principle of cooperative control between the shield and overburden roof is revealed, and the shield support capacity calculation method is summarized. Third, the quantitative criterion for disturbance degree of key stratum (KSDD) is proposed based on the key strata theory. Finally, several intelligent evaluation and analysis systems have been developed in terms of overburden breakage and shield support capacity, multi-information analysis of ground control, and disturbance degree of overburden. The research results may provide an essential reference for the development of intelligent ground control in the mining process of close-multiple coal seams

Jul 1, 2023

By Neal P. Cochran

The Office of Coal Research Program has been outlined in our Annual Report for a number of years and reported on by various members of the OCR staff as well as by our contractors. The program is national in scope and is intended to develop new and improved uses for our Nation's coal resources and to maintain coal in a favorable economic position, vis-a-vis, the other energy forms. A program has been developed that includes conversion of coal to gas, gasoline and other petroleum-type products, and to electricity. These projects are only one facet of the OCR program albeit an important one. In many of the conversion projects we have underway, original development work has been done with bituminous and sub-bituminous coal. It is the intention of this paper to present a general outline as to how lignite might fit into one or more of these projects as a raw material. Our national lignite reserves are vast in scope and this has been recognized in the OCR program by development of a project specifically for lignite and by including lignite as a test raw material in many other projects. Project Lignite is intended to develop the Cop Acceptor Process for conversion of lignite to a high B.t.u. gas. In this effort we have included the design, construction, and operation of a lignite gasification plant at Rapid City, South Dakota. The work is being conducted by the Consolidation Coal Company and is an outgrowth of their laboratory development of this process. The first portion of our effort included a detailed economic study of a somewhat arbitrary grouping of States designated Market Area A that could be expected to use gas manufactured in a lignite gasification plant. The area included the Dakotas, Minnesota, Nebraska, and Iowa. This geographical area could readily be served if a process could be developed for converting North Dakota's lignite reserves, estimated at 351 billion tons, to high B.t.u. gas. Our study showed that Market Area A had a potential commercial- industrial market of one trillion cubic feet of gas a year. To meet this demand, we believe that part of the load can be obtained from commercial lignite-to-gas plants. At the time of our original study, we concluded that gas could be delivered to the city gate in Market Area A at about 45¢. As a result of price escalation in the interim, our estimate today might be slightly higher, but not significantly so, since some parts of the process appear better today than they did at the time of the original projection.

Jan 1, 1968

By E. Yan, M. Mankosa, G. Luttrell

"During the past decade, column flotation cells have become widely accepted for upgrading ultrafine sulfide ores. However, the use of columns has been widely relegated to cleaner circuits due to their comparatively high selectivity derived from the use of wash water dispersed over a deep froth. High tonnage rates and low feed grades make using column technology in roughing and scavenger stages challenging due to the resulting size of the needed equipment. To specifically address this challenge, a new high-intensity flotation system known as the StackCell™ was developed. This technology makes use of a novel pre-aeration method coupled with froth washing to simultaneously provide improved flotation kinetics and selectivity. The novel aeration system provides efficient bubble-particle contacting thereby shortening the residence time required for particle collection. This article reviews the technical design features of this new flotation technology and presents recent data from in-plant pilot testing in a copper-sulfide application. INTRODUCTION Column flotation cells have become very popular in the minerals processing industry for cleaner circuits due to their ability to produce a high-grade froth concentrate via the use of froth washing (Luttrell et al., 1999; Kohmuench et al., 2004). The use of wash water minimizes the nonselective recovery of ultrafine impurities that are normally entrained into the froth product from conventional flotation machines. On the other hand, the unique design of a column cell typically requires a large tank volume. Column cells must be tall to ensure that the pulp residence time is long enough to offset their inherently slow flotation kinetics and to minimize internal mixing that is detrimental to overall cell performance. The tall design minimizes the total floor space required for the column installation, but substantially increases the foundation load. The large size of the column tank can also create issues during fabrication, transportation and installation. To address these concerns, the engineering team at Eriez Manufacturing developed a next-generation flotation technology called the StackCell?. This high-intensity flotation machine was designed to provide column-like separation performance within a very compact volumetric footprint. This article describes the key working features of this new technology and provides data from recent pilot-scale tests conducted in gold and copper-sulfide applications"

Jan 1, 2016

By S. K. Kawatra, S. K. Valluri, S. J. Root

Common carbon dioxide capturing reagents, such as amines and sodium hydroxide, are expensive, toxic, and energy intensive to regenerate. We have added frothers to a sodium carbonate solution in order to increase the surface area available for CO2 transport within the packed bed of a counter current scrubbing column. Addition of frothers has improved the performance of sodium carbonate scrubbing solutions to be on par with sodium hydroxide scrubbing solutions. This novel enhancement of a relatively inexpensive CO2 capture-regeneration cycle shows potential to allow plants to turn a profit by sequestering a waste product. These results are discussed in detail in the following manuscript. INTRODUCTION The combustion of fossil fuels converts chemical energy to thermal energy. CO2 is produced as a byproduct of the reaction. 80% of the world’s electricity is produced by using this thermal energy to power a generator, accounting for 40% of global carbon dioxide emissions. In an effort to stabilize the rising atmospheric CO2 levels, researchers are investigating the application of carbon capture and storage (CCS) systems in power plants. [1] Efforts to capture CO2 at some power plants have been successful, but the cost of installing and operating the required equipment is high. As such, very few power plants have CCS systems. If CO2 can be captured and processed into a product that can be sold at a profit, installing CCS systems in power plants will be a very attractive business decision. In order for the sale of captured CO2 to become a profitable venture, the cost of capturing the CO2 from a flue gas must be reduced. BACKGROUND The most common method for separating CO2 from a flue gas is by passing it through a counter-current packed bed scrubbing column. The flue gas enters the bottom of a column while a solution of a chemical with properties advantageous to the absorption of CO2 is pumped to the top. The fluids interact in a packed bed, where the CO2 is transported from the gas to the liquid. CO2 is an acid gas, so it is common for the scrubbing solution to be alkaline in nature in order to neutralize the carbonic acid that is formed when it is dissolves into water. The exhaust exits the top of the column free of carbon dioxide, which exits the column in the scrubbing solution, reacting or complexing with the absorbent. Figure 1 is a schematic drawing of a CO2 scrubbing column. It shows the molar flowrates and compositions of the gas and liquid at the bottom [1], the top [2], and an arbitrary height in the column [Z]. [2,15] L is the molar flowrate of liquid at any point in in the column. G is the molar flowrate of gas at any point in the column. Since the CO2 is transported from the gas to the liquid, L and G are variable with respect to height. To simplify calculations, the CO2 free molar flowrates Ls and Gs are often used. X is the fraction moles of aqueous CO2 per mole of CO2 free liquid. Y is the fraction moles of gaseous CO2 per mole of CO2 free gas. Figure 2 is a composition diagram of the scrubbing column depicted in figure 1.

Jan 1, 2019

By J. J. Wallaert

The decreasing supplies of natural gas and low-sulfur crude oil available for electric power generation in the United States will unquestionably shift the emphasis to nuclear and coal fired steam power plants in the immediate future. Failure to do so will ensure our dependence on mid-east low sulfur crude oil comprising some 70% of the known world reserves, and imported liquid natural gas. By contrast, the United States has 43% of the known world reserves of anthracite, bituminous and semi-bituminous coal and 48% of all known coal reserves of the world including lignite. It is evident, therefore, that coal is alive and well and will continue to be a significant energy source for the production of electricity for many years. Of course, concern for our environment and the development of new technologies will ultimately curtail the utilization of coal for the generation of bulk power, but information released by the National Electric Reliability Council and the Federal Power Commission is worth repeating. In the year 1972 the total capacity of generating units in the United States was 379,552 Mw of which 149,974 Mw, or 39.5% of the total, was produced by coal fired steam turbines which consumed 344,700,000 tons of coal. New capacity additions planned or in construction show that in the year 1981 our total generating capacity will be 843,503 Mw, of which 257,995 Mw, or 30.6% of the total, if from coal only. Translating this increase into terms meaningful to the bulk material handling industry suggests that ten years from now the utility industry will require 590,000,000 tons of coal per year - a monumental task - if we are to sustain our current demand rate for power.

Jan 1, 1973

Powder River Basin (PRB) mines were originally built to serve power plants designed specifically for their coal. Sulfur was the major concern, with BTU and sodium limiting the market for some. The Clean Air Act has extended the PRB market into plants converting from other coals. These new customers are more sensitive to constituents affecting boiler and precipitator performance. At the same time, the prospect of deregulation is forcing power companies to control cost more stringently than ever. Jacobs Ranch Mine has responded to the changing marketplace with an expanded coal quality and customer service program.

Jan 1, 1998

Microwave pretreatment can improve grindability by weakening brittle particulate material prior to size reduction. The differential thermal expansion experienced by multiphase materials during rapid heating can also promote damage in the grain-boundary region, which may ultimately translate into enhanced liberation. The effect of microwave pretreatment on the breakage characteristics of different ores has been studied using the Ultrafast Load Cell. The energy accumulated during impact (fracture energy) and the particle stiffness have been measured for untreated and microwaved ore samples. It has been observed that microwave pretreatment can weaken brittle multiphase particulate material, as observed by reductions in fracture energy and increase in damage.

Jan 1, 1996

By J. E. Lees

Advanced remote sensing can be a powerful new information tool to help private and public entities make better environmental and resource management decisions. However, some regulated entities are reluctant to develop or use this tool because of their concerns that it will lead to increased risks and costs of environmental legal liability. They fear that new ways of monitoring the environment will increase liability, undermine existing enforcement agreements, reopen compliance agreements, and generally provide a competitive disadvantage to early adopters by accelerating environmental cleanup costs. Others counter that the increased risks are marginal, and that several advantages outweigh these risks, including the opportunity to more effectively manage environmental operations, target and set priorities, measure and track management and compliance effectiveness, provide more defensible environmental assessments and baseline conditions, make and defend optimal siting decisions, and avoid or resolve environmental disputes. This paper offers strategic advice on ways regulated entities can enjoy the benefits of these powerful new information tools while mitigating down-side legal and compliance risks as much as possible.

Jan 1, 1999

By Pierre Longtin

"Replacing the aging roadway access to the iconic Golden Gate Bridge, thereby ensuring traffic safety and robustness in case of seismic occurrences, provided an opportunity for major design improvements as well as the development of a parkway that would include the construction of four new tunnels. With an eye to the future, the Doyle Drive replacement project aimed to meet the highest standards for environmental stewardship beyond regulatory requirements. Understanding that lighting equipment is the tunnel‘s subsystem that uses the most energy, the operator was looking for a sustainable solution to light the tunnels. An Intelligent Lighting Control System (ILCS), designed specifically for road tunnels, was acquired to individually control the almost 2000 luminaires lighting the four tunnels. This paper will show the results in terms of energy and operational savings generated over the nine months of operation between the commissioning and the conference in April 2016. INTRODUCTION Electrical & mechanical (E&M) equipment represents an average of 10 % of a tunnel total construction cost. Once the civil infrastructure completed, E&M equipment drives the main part of the expense during a tunnel useful life. Table 1 below describes the impact of various types of energy consumption and their cost impact in tunnels of less than 500 m. It is clear that lighting is the sub-system that requires the most energy. A good lighting strategy is the key to reducing energy consumption due to lighting and a viable solution that will bring important savings in tunnel operations.With a price of $0.14/kWh in California and a planned increase between 3% and 6% per year during the period 2013-2040, the tunnel operators could not afford to overlit the tunnels—particularly when they have to operate it for the next 30 years. However, they also need to maintain the right lighting level to ensure driver safety all the time. The Presidio Parkway project includes the Battery tunnels, which are 240 m (790 feet) and 230 m (750 feet) in length, and the Main Post tunnels, which are 280 m (920 feet) and 315 m (1030 feet) in length."

Jan 1, 2016

By M. G. Gorman

The effects of particle size, particle shape and degree of aggregation on n-dodecylamine flotation of -20 µ m quartz and glass beads were studied. A microflotation cell suitable for use with very fine particles was used in the flotation experimentation. Degree of agglomeration of particles was estimated by comparing size distributions of the quartz and beads in a dispersed system to size distributions in systems in which the collector was present. Results obtained show that in such flotation systems the fine particles are not generally present as individual particles during flotation but rather as aggregations. However, the quartz floats more readily than the beads indicating that there are some shape effects in the systems, considering the large specific surface areas of the materials it also appears that substantial amine consumption in the systems may limit flotation or lead to a requirement of greater reagent dosage for equivalent flotation to that tor larger particles.

Jan 1, 1990

By Björn Johansson

"SUMMARY Every tunnel designer has to consider the power of water ingress when designing a new tunnel. Either you choose solutions with simple methods to divert the ingress water or a robust system with the intention that it will give gain on low maintenance costs and a long lifetime. This article describes a new method to divert ingress water in a robust way and more economical than traditional concrete lined tunnels. This system is based on a bolt grid suspending a water tight membrane, which is reinforced and covered with sprayed concrete. The method has been in limited use in Sweden since 2005 and with continuous improvement, still going on, it is now applied for the large project “Stockholm Bypass”, a 21km long highway project. TUNNEL MAINTENANCE RELATED TO WATER INGRESS The Swedish Transport Administration maintain approximately 190 various tunnels that is constructed by a number of different methods, (Swedish Transport Adm 2015). Commonly the ground conditions are good and fairly low ground support is needed. Contrary water and winter conditions can be sever, which gives high impact onto the tunnel design and in particular methods to protect against “frost and water ingress”. During a tunnels lifetime it is common that maintenance related to water ingress occurs several times and sometimes frequent occasions every year. Such maintenance costs and consequences of lost open time for the tunnel can rapidly become higher than the initial cost of the tunnel. Thereby it is obvious that spending time during design to evaluate requirements for a suitable system against water ingress is preferred. Icicles Icicles are formed when water is below freezing degrees and drips or run from an ingress point. At very cold conditions also water flows running at high velocity freeze into ice and a rapid growth can appear. If the integrity of the tunnel traffic area is interfered by icicles they urgently have to be removed before they cause an accident. Typically the tunnel or a part of the tunnel must be closed to do such maintenance. TUNNELS FROST AND WATER INGRESS PROTECTION IN SWEDEN In Sweden methods to perform “frost and water ingress protection” are primary developed for drill and blast tunnels as it is most common tunneling method. The foundation Swedish Rock Engineering Research has done a comprehensive report SveBeFo Rapport 77 that describes water and frost prevention in Swedish tunnels up to year 2005. Below is only slight description of those various methods. Lately some more attention is paid to concrete lined tunnels made by TBM since TBMs successfully built water tight tunnels in City Tunnel (Malmö) and Hallandsås Project. When environmental demands require maintained ground water levels, water tight tunnels made by pressurized concrete lining becomes more economical and on the same time also becomes protected from icicles and water drips."

Jan 1, 2016

By Gerald H. Luttrell

The determination of mass balances is the first step in analyzing the performance of processing circuits. Although conceptually very simple, the mathematics associated with mass balances can be cumbersome when conflicting data sets and/or complex circuits are evaluated. Fortunately, many of the spreadsheet programs available today include powerful search routines which can be adapted to solve common mass balance problems. To demonstrate these capabilities, a generalized mass balance program has been developed using the Microsoft Excel? spreadsheet. Compared to commercial programs, the spreadsheet format is user-friendly, more versatile and easier to customize. This paper reviews the mass balance problem and describes how spreadsheet tools can be used to reconcile conflicting data.

Jan 1, 1996

By S. C. Howell

The mining of taconite, to provide feed for a processing plant, requires that the flow of material continue uninterrupted. This means first, that the crude must be of a size acceptable to the primary crusher in order to reduce the delays caused by plugging the crusher with chunks. Secondly, elimination of oversize in the pit will reduce costs of all wear parts used in the mining and processing of taconite. Savings in wear parts is readily recognized in dipper teeth, bases, buckets, truck boxes, and crusher parts, both primary and secondary. During the early days of taconite mining, it was soon recognized at reserve mining company's Babbitt operations that experience in mining other ores was not always (or ?necessarily??) Applicable to excavating taconite. This was especially true in drilling and blasting. Blasting of small tonnages in single or double rows simply filled the pit with scattered chunks and provided very shallow banks for shovel loading. It also created problems for the jet piercers, since all drilling had to be performed in fractured areas. Drilling efficiency suffered and costs were extremely high. Shovel and truck efficiencies were also low and again costs were high. A high percentage of secondary breakage was required. This necessitated the use of numerous man hours to jackhammer holes in chunks, preparatory to loading and blasting. After the chunks were reduced, bull- dozer and grader hours were needed to pile the taconite for acceptable shovel loading.

Jan 1, 1968

By J. G. Pippenger

The Coteau Properties Company's Freedom Mine is a surface lignite mining operation utilizing large draglines, trucks and shovels, tractor-scrapers, and bulldozers to uncover a single coal seam. In 1989, a work order system was instituted to record data by equipment type, cost, productivity, and distance, and to provide historical information for planning the most efficient and economic use of each equipment type in the mining operation. This report explains how the work order system was initiated, what data is tracked, and how the data is utilized for equipment and project scheduling.

Jan 1, 1994

By L. M. Pruett

The Arizona Legislature is currently in the process of considering mined land reclamation legislation in the 1994 legislative session. A bipartisan legislative study committee has drafted proposed mined land legislation. The committee has attempted to craft legislation that is appropriate for the unique conditions in Arizona. Existing Arizona and federal laws and regulations extensively regulate the environmental performance of mines in the state to protect public health, safety and the environment. The proposed mined land reclamation legislation does not replace or duplicate these statutory provisions relating to environmental protection. Instead, the purpose of the proposed legislation is to provide for the reclamation of land that is being mined and to fill the gap in existing laws by requiring the reclamation of land that currently is being mined or that has been mined since 1986 to provide for future land use. The legislation would require an operator to submit a reclamation plan describing the exploration operations, mining operations, post-mining land use and the proposed reclamation measures for review by a state agency. Financial assurance also would be required in an amount such that a third party could complete the approved reclamation measures. Arizona's mined land reclamation legislation would recognize Arizona's leading role in hard rock mining and emphasize the mining industry's economic importance to Arizona and the nation. Because mining operations necessarily require disturbing the surface of the earth to extract valuable minerals, reclamation requirements would be adapted to different conditions and would vary depending on site-specific conditions and on the commodity being mined. The current proposal does not identify the state agency that will administer the mined land reclamation program and approve reclamation plans, substantial changes to plans, and transfers of reclamation plans to other operators.

Jan 1, 1994

By Don Muraoka

Soda ash, anhydrous sodium carbonate, is produced from underground trona deposits occurring in the Green River Sasin of Southwestern Wyoming. Stauffer Chemical Company of Wyoming, a jointly owned subsidiary of Stauffer Chemical Company and Rocky Mountain Energy Company mines the trona and processes it into high-purity soda ash. Stauffer Wyoming has been in operation since 1962 with a current production capacity of approximately 2.2 million tonnes (2 million short tons) per year of soda ash. The Refinery has five parallel operating trains utilizing the monohydrate process which is a series of chemical processing unit operations described below. Screening and Crushing the Trona The mined trona is brought to the surface in two counterbalancing ore skips. The ore is initially screened with Refinery feed, less than peagravel size material, entering the process while the oversize is conveyed to an outdoor stockpile.

Jan 1, 1984